1. Field of the Invention
This invention is related to the storage and transfer of components, such as electrical connectors, in transfer tubes, trays or containers and to the use of these containers with automated fabrication and assembly equipment.
2. Description of the Prior Art
Thermoformed tubes, trays or containers are commonly use to store and ship components and devices of different types including the storage and shipping of a large number of relatively small items in channels in a single tube, multi-tube assembly or tray. For example electrical components, such as electrical connectors, are commonly shipped in this manner. These types of containers provide a cost effective package that adequately protects these components or connectors during normal handling.
Most prior art tubes and trays of this type are disposable containers that are manufactured for the lowest possible cost. However, these containers are increasingly used as in-process packages in which various components are loaded and unloaded a number of times. For example, components packaged in these containers or trays may require several different manufacturing steps, such as molding and terminal insertion, that take place on different manufacturing lines and often at different manufacturing facilities. Testing and inspecting and other manufacturing steps must also be performed on the components. Finally the components must be shipped to a customer who in turn will assemble the components in a final or intermediate assembly. For example, it is common practice to use thermoformed tube assemblies of this type to feed electrical connectors to a manufacturing station in which the connectors are soldered to a printed circuit board.
A cost effective way of transporting or transferring these components or connectors between various manufacturing operations and to the customer is to use the same multi-tube assembly or tray and to repeatedly load and unload components and subcomponents in the same trays. If possible the tube assemblies or trays should then be re-used after the components have been unloaded for a final time. It is common for customers to ship empty containers back to the manufacture where the containers are repeatedly re-used as many times as possible.
For high volume assembly operations loading and unloading is typically performed by automatic equipment, such as robotic or pick and place equipment. Therefore the tubes or trays must be inherently robust and dimensionally stable. If the tubes or trays are susceptible to damage during use, proper alignment for loading or unloading becomes increasingly problematic. Furthermore if the single tubes or channels in multi-tube assemblies become distorted, the components may hang up in the channels resulting in incomplete loading and unloading.
Although robust construction is one consideration that is important to maintaining dimensional stability for re-usable in-process tube assemblies, fabrication considerations are also important. For example, the common way in which such tubes are fabricated is to bond two thermoformed members together. An RF welding process can be used to produce heat for bonding the thermoformed members. Although this produces a strong bond, the addition of heat also introduces stresses into the thermoformed plastic. One of the two sheets is heated more than the other during bonding, and the differential expansion induces stresses in the final product. These stresses can soon result in warping, bowing or other dimensional irregularities. The larger the tube assembly, and therefore the larger the number of components that can be stored, then the more these stresses will add up or accumulate to cause dimensional distortion that can affect the performance and reliability of these thermoformed packages
U.S. Pat. No. 5,012,925 shows one package that is formed by a thermoformed top that is permanently bonded to an extruded member to form a multi-tube assembly. Similar prior art configurations in which thermoformed top and bottom members are permanently bonded are also used for in-process packaging. These prior art thermoformed packages, however, are derived from designs where the primary purpose was a disposable rather than a re-usable package. Therefore these prior art packages lack dimensional stability because of the stresses induced in bonding and the robustness that is needed for high volume in process use. Therefore excessive manufacturing problems are caused when the components are not properly loaded or unloaded. These problems will require intervention by the operator and often result in either discarding of components in partially filled packages or in manufacturing problems in final assembly. For example if an electrical connector is not properly fed from a tube to automatic assembly equipment, the connector may not be properly inserted into the final assembly, such as a printed circuit board. In either case increased manufacturing costs or reliability problems can ensue.